This came up in the "Spiritual Power" thread and I thought I'd start a new thread rather than hijacking that one--

Where did O-Sensei pick up his swordwork? Is anything really known about it?

What I've heard, without checking references, is that at least one master swordsman said that Ueshiba was the best swordsman in Japan. I've heard that he said Aikido techniques are based on sword techniques ("When you have no sword, move like you have a sword.") And he regularly demonstrated and taught swordwork.

But I've also heard that there's no real evidence of him being signed up with any sword school or taking lessons from a known master. So where did it come from?